The invention relates to filtration devices and systems in residential and commercial buildings for heating, ventilating and air conditioning (HVAC) the buildings.
A common conventional air filter, such as a furnace air filter, includes a porous filtration media that is oriented transverse to a path of air or other gas flow during use, such as at a position just upstream of a furnace's blower. A common configuration for such a filter includes a slot formed along the path of a cold air return duct. The slot is slightly thicker than the filter and is about as wide and deep as the filter. Therefore, a filter can be inserted into the slot through an opening on one side until the filter is completely inserted. Then a covering over the slot is closed and the furnace is used in a conventional manner.
Air drawn into the furnace for heating in the cooler seasons, and for cooling in the warmer seasons, passes through the porous filtration media to filter the air of particles greater than a predetermined size. The filtration of air keeps the operating components of the furnace and blower from being damaged by abrasion and/or corrosion caused by the particulate matter, and serves to “clean” the air in the building in which the furnace operates so that humans or animals breathe healthier air. With the configuration described above, air filters can be removed from the slot, when they become coated with particulate and reach the end of their useful lives, so they can be replaced as described above.
Because conventional air filters have a preferred orientation relative to the direction of air flow, they must be placed in the slot in the correct orientation. As an example, most air filters have an upstream side and a downstream side, and if air flows through the filter in the direction opposite the preferred direction, the filter does not operate with optimal efficiency. However, conventional slots for air filters permit the filter to be inserted in correct and incorrect orientations.
The need exists for a filter and a filter apparatus that encourages and/or requires the correct orientation of the filter relative to air flow.